When a “blade-out” event occurs in an aircraft engine, it is critical that the aircraft have “fly-home” capability (i.e., the ability to return safely to the ground under FAA rules). The ability of the engine nacelle to tolerate damage and maintain its structural integrity during a blade-out event is critical to the fly-home capability of an aircraft.
Some known engine nacelle inlets include acoustic inner barrels composed of multiple annular segments secured by splice joints provided with fasteners. In addition to fastening adjacent annular segments of the acoustic inner barrel, the splice joints function to limit the propagation of damage through the barrel. Thus, the “damage-stopping” splice joints help preserve the structural integrity of the acoustic inner barrel, and therefore, the entire nacelle, during a blade-out event. Examples of multi-piece acoustic inner barrels are disclosed in U.S. Published Application No. 2008/0017442, which is assigned to Rohr, Inc.
In some modern aircraft, the engine nacelle inlet includes a 360-degree, one-piece (i.e., formed as a single annular segment) acoustic inner barrel composed of a cellular core or core assembly (SDOF or DDOF core blanket) disposed between inner and outer skins. The cellular core may be constructed of either a metallic or a composite material, such as graphite-epoxy or the like, and may include an inner array of cells and an outer array of cells separated by a septum. The inner and outer skins are also made of the composite material. As a result of their monolithic design, one-piece acoustic inner barrels lack the damage-stopping splice joints of multi-segment acoustic barrels. Therefore, providing sufficient tolerance to damage during a blade-out event is a primary concern with 360-degree, one-piece acoustic inner barrels.
It is desirable to provide a 360-degree, one-piece acoustic inner barrel for an aircraft engine nacelle that exhibits improved cracking, disbond, and delamination resistance, to mitigate a blade-out event.